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Sprinkler System Protection Area Limitation

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Radwan

Mechanical
Feb 2, 2003
4
According to NFPA-13, section 5-2 the sprinkler system protection area limitation is 52,000 sq. ft.(ordinary hazard) on each floor, for any one system riser. Is there a limitation on the number of risers in a sprinkler system? What's confusing me is that the flow requirement for a sprinkler system, when determined by the Area/Density method (NFPA-13, section 7-2.3.2.1),is lmited to a maximum value, but there's no limitation I can see on the size of the system, as long as risers are added! Does that mean I can protect an area, regardless of its size, by a limited flow? In other words, is the flow requirement for a one-riser system covering an area of 52,000 sq. ft. the same as the flow requirement for a ten-riser system covering an area of 520,000 sq. ft.?
 
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You are confusing the maximum area of coverage for a sprinkler system with the area of demand. The water demand is based on the area of demand and the density curve for the particular hazard. The maximum area of coverage of a sprinkler system is 52,000 sq ft for light or ordinary and 40,000 sq ft for extra hazard or special hazards. Therefore, each riser can supply only the 52,000/40,000 sq ft and you can have an umlimited number of risers in a building, but you only calculate the water demand to control a fire for a much smaller area (usually 2000 to 3000 sq ft) depending on the hazard.

James D. Kieffer, PE
Kieffer & Associates Inc.
 
How can I decide how many risers to install for an area with 50,000 sq ft? Just one is enough since the area is within the limitation 52,000 sq ft? Please help!
 
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